The current work represents a continuation of investigations of biochemical function in relation to fine structural elements studied by combining biochemistry, organometalo chemistry, cytochemistry and electron microscopy. The work covers several areas now in progress and are natural extensions of previous accomplishments. These include: (1) studies on membrane biogenesis. These experiments have focused on the sites of synthesis and assembly of phospholipid and of enzymatic proteins. Although 4 systems undergoing membrane biogenesis have been studied, most of the work now focuses on the plasma membrane of the secretory cells of the salt gland of the salt stressed duckling. (2) Continued studies of enzymes concerned with phospholipid synthesis (Phosphatidic acid phosphatase and CDP--choline transferase) and of Na ion K ion ATPase. (3) Studies of the composition in relation to the fine structural organization of membranes. These studies involving newly synthesized reagents for the localization of specific phospholipids, cholesterol and of groups in protein. (4) Finally, studies are continuing on isolated capillary endothelial cells with reference to understanding the structural and functional differences between endothelial cells of different capillary beds as well as the phenomenon of micropinocytosis. Concerning the later, attempts will be made to isolate micropinocytic vesicles by centrifugation techniques so as to biochemically and cytochemically characterize these elements. The undersigned agrees to accept responsibility for the scientific and techniques conduct of the project and for the provision of requiring progress reports if a grant is awarded as a result of this application.